1. Field of the Invention
The present invention relates to a multiple oscillation-type generator, and more particularly to a multiple oscillation-type generator configured to generate electric power by repeatedly ascending and descending inside a flowing fluid by means of flow energy of the fluid.
2. Description of the Prior Art
Tidal stream generation refers to a type of generation using the flow of seawater and, unlike tidal power generation which installs a breakwater near a shore and generates electric power using the difference of ebb and flow tides, utilizes fast sea currents and rotates turbines installed in the sea, without installing a dam or a breakwater in the corresponding area.
Since there is no need to build a breakwater, the tidal stream generation costs less than the tidal power generation, allows free passage of ships, and has neither interference with movements of fishes nor influence on surrounding ecosystems, making it eco-friendly.
In this regard, US Patent Publication No. 2013-0202407 entitled “OSCILLATING HYDROFOIL, TURBINE, PROPULSIVE SYSTEM AND METHOD FOR TRANSMITTING ENERGY” discloses a power transmission device including a vertical post and first and second hydrofoils which extend from the post in the horizontal direction and which are configured to be rotated by flow of a fluid and moved along the longitudinal direction of the post.
The power transmission device disclosed in US Patent Publication No. 2013-0202407, more specifically, includes a first hydraulic cylinder provided inside the post and configured to operate as the first hydrofoil reciprocates and a second hydraulic cylinder provided inside the post and configured to operate as the second hydrofoil reciprocates, as in the case of the first hydraulic cylinder. As the first and second hydrofoils reciprocate linearly, the first and second hydraulic cylinders convert kinetic energy, which results from a movement of the internal fluid, into mechanical work and produce electric power.
In addition, Registered U.S. Pat. No. 8,469,663 and US Patent Publication No. 2013-0216381 disclose technology for driving a turbine using the linear reciprocating movement of a foil resulting from flow energy of a fluid, as well as a generator configured to drive a turbine using the rotational reciprocating movement of a foil.
Conventional power transmission devices disclosed in US Patent Publication No. 2013-0202407, Registered U.S. Pat. No. 8,469,663, and US Patent Publication No. 2013-0216381 change the angle between the foil and the direction in which the fluid flows, and thereby generate lift, which results from flow energy of the fluid, in the direction of reciprocating movement of the foil.
In the case of such a power transmission device having a foil configured to reciprocate using flow energy of the fluid, the generation efficiency of the turbine improves in proportion to the magnitude of lift generated by the foil, making the foil shape design critical.
However, conventional power transmission devices disclosed in US Patent Publication No. 2013-0202407, Registered U.S. Pat. No. 8,469,663, and US Patent Publication No. 2013-0216381 have a problem in that the fixed foil shape prevents the magnitude of lift, which acts on both surfaces of the foil, from increasing beyond a predetermined range, placing a limit to increasing the magnitude of lift by using the foil shape as a parameter.
There is also a problem in that, when additional power is used to variably change the foil shape, in order to generate larger lift acting on the foil, the generation efficiency of the turbine decreases in proportion to the amount of additionally used power.